1. Field of the Invention
The present invention relates to a preform carrying apparatus for carrying a preform along a passage on which working stations are provided.
2. Description of the Related Art
In order to form a hollow product such as a bottle as a final product, an apparatus for blow molding a preform (also called a "parison") obtained in advance by injection molding is adopted. The apparatus disclosed in Japanese Patent Laid-Open No. 89470/1975 is provided with a first passage which is capable of carrying a preform while rotating and heating it, and a second passage which receives the preform supplied from the first passage and carries a plurality of radially arranged blow molds while rotating them. In this apparatus, it is difficult to supply air and electric power to the blow molds carried under rotation, resulting in an expensive equipment cost. In this respect, the apparatus disclosed in Japanese Patent Laid-Open No. 297231/1989 is more advantageous. In this apparatus, a preform receiving station, a heating station, a blow molding station and an ejecting station are disposed on an endless passage in a fixed state and a preform is carried along the passage.
In carrying a preform to each working station, since it is necessary to stop feeding the preform during the processing time at each working station, it is necessary to carry preforms intermittently.
In the case of intermittent feeding, it is necessary to set the feeding stop time at the maximum processing time at one working station. It is therefore necessary to stop the feeding of a preform to each working station during a heating process, which generally takes the longest processing time, so that a long forming cycle is disadvantageously required. In addition, since the feeding stop time is determined by the processing time at one working station, setting of working conditions such as heating conditions at other working stations becomes very complicated. Furthermore, the control of intermittent feeding is more complicated than the control of continuous feeding and increases power consumption.